Chapter 23: The Respiratory System

1
Chapter 23 The Respiratory System
Primary sources for figures and content Marieb,
E. N. Human Anatomy Physiology. 6th ed. San
Francisco Pearson Benjamin Cummings,
2004. Martini, F. H. Fundamentals of Anatomy
Physiology. 6th ed. San Francisco Pearson
Benjamin Cummings, 2004.
2
The primary functions of the respiratory system.
3
The Respiratory System

• Cells produce energy
• for maintenance, growth, defense, and division
• through mechanisms that use oxygen and produce
  carbon dioxide

4
Oxygen

• Is obtained from the air by diffusion across
  delicate exchange surfaces of lungs
• Is carried to cells by the cardiovascular system
  which also returns carbon dioxide to the lungs

5
5 Functions of the Respiratory System

• External respiration
• - Provides extensive gas exchange surface area
  between air and circulating blood
• Pulmonary ventilations
• Moves air to and from exchange surfaces of lungs
• Protects respiratory surfaces from outside
  environment
• - dehydration, temperature changes, invasion by
  pathogens
• Produces sounds for communication
• Provide olfactory sensation Smell

6
Components of the Respiratory System
Figure 231
7
Organization of the Respiratory System

• The respiratory system is divided into the upper
  respiratory system, above the larynx, and the
  lower respiratory system, from the larynx down

8
Anatomy of Respiratory System

• 1. Upper Respiratory System
• Function to warm and humidify air
• Nose, nasal cavity, sinuses, pharynx
• 2. Lower Respiratory System
• Conduction portion
• Bring air to respiratory surfaces
• Larynx, trachea, bronchi, bronchioles
• Respiratory portion
• Gas exchange
• Alveoli

9
Alveoli

• Are air-filled pockets within the lungs
• where all gas exchange takes place

10
The Respiratory Epithelium
Figure 232
11
Respiratory Mucosa mucus membrane

• Lines conducting portion of respiratory system
• Epithelial layer
• pseudostratified columnar epithelium
• Usually ciliated
• Scattered goblet cells mucin production
• Areolar layer lamina propria (trachea, bronchi)
• Areolar connective tissue
• Mucus glands mucin
• Serous glands lysozyme
• Glands produce 1 quart mucus fluid/day
• Cilia move mucus to pharynx to be swallowed
• Cilia beat slow in the cold

12
Alveolar Epithelium

• Is a very delicate, simple squamous epithelium
• Contains scattered and specialized cells
• Lines exchange surfaces of alveoli

13
The Respiratory Defense System

• Consists of a series of filtration mechanisms
• Removes particles and pathogens

14
Components of the Respiratory Defense System

• 1. Mucus
• From goblet cells and glands in lamina propria,
  traps foreign objects
• 2. Cilia mucus escalator
• Move carpet of mucus with trapped debris out of
  the respiratory tract
• 3. Alveolar macrophages
• Phagocytose particles that reach alveoli
• 4. Filtration in nasal cavity removes large
  particles

15
Disorders of theRespiratory Defense System

• 1. Cystic fibrosis
• Cause ? Failure of mucus escalator
• Result ? Produce thick mucus which blocks airways
  and encourages bacteria growth
• 2. Smoking ? destroys cilia
• 3. Inhalation of irritants ? chronic inflammation
  ? cancer e.g. squamous cell carcinoma

16
The upper respiratory system and their functions.
17
The Upper Respiratory System

• Nose
• Nasal Cavity
• Pharynx
• -Nasopharynx
• -Oropharynx
• -Laryngopharynx

Figure 233
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1. The Nose

• Only external feature
• Air enters the respiratory system
• through external nares
• into nasal vestibule
• Space in flexible part, lined with hairs to
  filter particles, leads to nasal cavity
• Nasal hairs in nasal vestibule are the first
  particle filtration system

19
1. The Nose

• Functions
• Opening to airway for respiration
• Moisten and warm entering air
• Filter and clean inspired air
• Resonating chamber for speech
• Houses olfactory receptors

20
2. The Nasal Cavity

• The nasal septum
• divides nasal cavity into left and right
• Superior portion of nasal cavity is the olfactory
  epithelium ? provides sense of smell
• Nasal conchae (superior, middle, inferior)
  project into cavity on both sides
• Nasal conchae cause air to swirl
• Increase likelihood of trapping foreign material
  in mucus
• Provide time for smell detection
• Provide time and contact to warm and humidify air

21
2. The Nasal Cavity

• Hard and soft palate form floor
• Internal nares open to nasopharynx
• Mucosa has large superficial blood supply
• Function ? warm, moisten air
• Epistaxis nose bleed
• Paranasal sinuses in frontal, sphenoid, ethmoid,
  and maxillary bones
• Lined with respiratory mucosa
• Connected to nasal cavity
• Aid in warming/moistening air

22
2. The Nasal Cavity

• Hard palate
• forms floor of nasal cavity
• separates nasal and oral cavities
• Soft palate
• extends posterior to hard palate
• divides superior nasopharynx from lower pharynx
• Air flow ? Nasal cavity opens into nasopharynx
  through internal nares

23
3. The Pharynx

• A chamber shared by digestive and respiratory
  systems
• Extends from internal nares to entrances to
  larynx and esophagus
• Three Parts
• Nasopharynx
• Oropharynx
• Laryngopharynx

24
3. The Pharynx

• Nasopharynx air only
• Posterior to nasal cavity
• Pseudostratified columnar epithelium
• Closed off by soft palate and uvula during
  swallowing
• Pharyngeal tonsil located on posterior wall
• Inflammation can block airway
• Auditory tubes open here
• 2. Oropharynx food and air
• Posterior to oral cavity
• Stratified squamous epithelium
• Palatine and lingual tonsils in mucosa

25
3. The Pharynx

• 3. Laryngopharynx food and air
• Lower portion
• Stratified squamous epithelium
• Continuous with esophagus

26
Why is the vascularization of the nasal cavity
important?

1. It heats incoming air.
2. It moisturizes incoming air.
3. It nourishes nasal epithelial cells.
4. All of the above.

27
Why is the lining of the nasopharynx different
from that of the oropharynx and the
laryngopharynx?

1. Nasopharynx lining is not subjected to food
   abrasion.
2. Nasopharynx lining must withstand temperature
   extremes.
3. Nasopharynx must be protected from drying out.
4. All of the above.

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The lower respiratory system and their functions.
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Air Flow

• From the pharynx enters the larynx
• a cartilaginous structure that surrounds the
  glottis

30
4. Larynx
Figure 234
31
4. Larynx voice box

• Hyaline cartilage around glottis
• Opening form laryngopharynx to trachea
• Functions of larynx
• Provide continuous airway
• Act as switch to route food and air properly
• Voice production
• Contains epiglottis
• Elastic cartilage flap ? covers glottis during
  swallowing

32
The Glottis
Figure 235
33
4. Larynx voice box

• Folds of epithelium over ligaments of elastic
  fibers create focal folds/cords
• Vocal cords project into glottis
• Air passing through glottis vibrates folds
  producing sound
• Pitch ? Controlled by tensing/relaxing of the
  cords
• Tense narrow high pitch
• Volume ? Controlled by the amount of air
• Sound Production ? phonation

34
4. Larynx voice box

• Speech
• Formation of sound using mouth and tongue with
  resonance in pharynx, mouth, sinuses and nose
• Laryngitis
• Inflammation of vocal folds
• Cause ? infection or overuse that can inhibit
  phonation

35
When the tension in your vocal folds increases,
what happens to the pitch of your voice?

1. It rises.
2. It falls.
3. Nothing happens.
4. It squeaks and cracks.

36
5. Trachea
Figure 236
37
The Trachea

• Attached inferior to larynx
• Walls composed of three layers
• 1. Mucosa
• Pseudostratified columnar epithelium, goblet
  cells, lamina propria, smooth muscle and glands
• 2. Submucosa
• CT with additional mucus glands
• 3. Adventitia
• CT with hyaline cartilage rings (15-20) ? keep
  airway open, C-shaped
• Opening toward the esophagus to allow expansion,
  ends connected by trachealis muscle

38
6. Primary Bronchi

• Trachea branches into the Right and left primary
  bronchi
• Similar structure as trachea
• No trachealis muscle
• Right steeper angle
• Enter lungs at groove (hilus)
• Along with blood and lymphatic

39
Hilus

• Where pulmonary nerves, blood vessels, and
  lymphatics enter lung
• Anchored in meshwork of connective tissue

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Gross Anatomy of the Lungs
Right 3 lobes Left 2 lobes
Figure 237
41
6. Primary Bronchi

• Lungs have lobes separated by deep fissures
• Inside lungs bronchi branch, get smaller in
  diameter
• Branch 23 times creating the bronchial tree
• As bronchi get smaller, structure changes
• Less cartilage in adventitia
• More smooth muscle in lamina propria
• Epithelium is thinner, less cilia, less mucus

42
Bronchitis

• Inflammation of bronchial walls
• causes constriction and breathing difficulty

43
Relationship between Lungs and Heart
Figure 238
44
7. Terminal bronchiole
Smallest bronchi of Respiratory Tree
Figure 239
45
7. Terminal bronchiole

• Smallest Bronchi
• No cartilage
• Last part of conduction portion
• Trachea, Bronchi and Bronchioles innervated by
  ANS to control airflow to the lungs
• ANS Regulates smooth muscle
• controls diameter of bronchioles
• controls airflow and resistance in lungs
• Sympathetic ? bronchodilation
• Parasympathetic ? bronchocontriction
• histamine release (allergic reactions)

46
Asthma

• Excessive stimulation and bronchoconstriction
• Activated by inflammatory chemicals (histamine)
• Stimulation severely restricts airflow
• Epinephrine inhaler mimics sympathetic ANS ?
  bronchodilation

47
7. Terminal bronchiole

• Each terminal bronchiole delivers air to one
  pulmonary lobule, separated by CT
• Inside lobule, terminal bronchiole branches into
  respiratory bronchioles
• No cilia or mucus
• Each respiratory bronchiole connects to alveolar
  sac made up of many alveoli

48
The Bronchioles
Figure 2310
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8. Alveoli
Figure 2311
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8. Alveoli

• Wrapped in capillaries
• Held in place by elastic fibers
• Three cell types
• 1. Type 1 cells gas exchange
• Simple squamous epithelium, lines inside
• 2. Type II cells surfactant
• Cuboidal epithelial cells produce surfactant
• Phospholipids proteins
• Prevent alveolar collapse, reduces surface
  tension
• 3. Alveolar macrophages Phagocytosis
• Phagocytosis of particles

51
8. Alveoli

• Alveoli connected to neighbors by alveolar pores
• Equalize pressure
• Gas exchange occurs across the respiratory
  membrane (0.5µm thick)
• 3 Parts of the Respiratory Membrane
• Squamous epithelial lining of alveolus
• Endothelial cells lining an adjacent capillary
• Fused basal laminae between alveolar and
  endothelial cells

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Respiratory Distress

• Difficult respiration
• due to alveolar collapse
• caused when septal cells do not produce enough
  surfactant

53
Disorders of the Alveoli

• 1. Pneumonia
• Inflammation of lungs from infection or injury
• causes fluid to leak into alveoli
• compromises function of respiratory membrane ?
  prevents gas exchange
• 2. Pulmonary embolism
• Block in branch of pulmonary artery
• Reduce blood flow
• Causes alveolar collapse

54
Gross Anatomy of Lungs
Figure 238
55
Gross Anatomy of Lungs

• Concave base, rest on diaphragm
• Right 3 lobes
• Left 2 lobes (accommodates heart)
• Housed in pleural cavity
• Cavity lined with parietal pleura
• Lungs covered by visceral pleura
• Both pleura produce serous pleural fluid to
  reduce friction during expansion
• Pleurisy
• Inflammation of pleura
• Restrict movement of lungs ? breathing difficulty

56
Why are the cartilages that reinforce the trachea
C-shaped?

1. To prevent tracheal crushing.
2. To conform to thoracic cavity shape.
3. To allow room for esophageal expansion.
4. To allow normal cardiac functioning.

57
What would happen to the alveoli if surfactant
were not produced?

1. The alveoli would contract.
2. The alveoli would collapse.
3. The alveoli would expand.
4. The alveoli would pop.

58
What path does air take in flowing from the
glottis to the respiratory membrane?

1. larynx, trachea, bronchi, alveolar duct, alveolar
   sac, respiratory membrane
2. larynx, trachea, alveolar duct, bronchioles,
   respiratory membrane
3. trachea, bronchi, larynx, bronchioles, alveolar
   duct, alveolar sac,
4. larynx, trachea, bronchioles, alveolar duct,
   bronchi, alveolar sac, respiratory membrane

59
List the functions of the pleura. What does it
secrete?

1. prevents cardiac friction secretes mucus
2. prevents respiratory friction secretes pleural
   fluid
3. protects lungs from drying out secretes mucus
4. protects heart and thoracic cavity secretes
   enzymes

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Respiratory Physiology
61
Respiration

• External Respiration
• Includes all processes involved in exchanging O2
  and CO2 with the environment
• Internal Respiration
• Also called cellular respiration
• Involves the uptake of O2 and production of CO2
  within individual cells

62
External Respiratory Physiology

• 3 steps of respiration
• 1. Pulmonary ventilation breathing
• 2. Gas Diffusion/Exchange, across membranes and
  capillaries
• 3. Gas Transport to/from tissues
• between alveolar capillaries
• between capillary beds in other tissues

63
1. Pulmonary Ventilation

• Movement of air into/out of alveoli
• Visceral pleura adheres to parietal pleura via
  surface tension
• Altering size of pleural cavity will alter size
  of lungs
• Pneumothorax
• Injury of thoracic cavity
• Air breaks surface tension ? lung recoil
  atelectasis, or collapsed lung

64
1. Pulmonary Ventilation

• Mechanics of breathing
• Boyles law gas pressure is inversely
  proportional to volume
• Defines the relationship between gas pressure and
  volume
• P 1/V
• Air flows from area of high pressure to low
  pressure

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Gas Pressure and Volume
Figure 2313
66
Mechanisms of Pulmonary Ventilation
Figure 2314
67
Mechanisms of Pulmonary Ventilation

• Diaphragm
• Contraction of diaphragm pulls it toward abdomen
• Lung volume INCREASE
• Air pressure DECREASE
• Air flow ins
• Relaxation causes diaphragm to rise in dome shape
• Lung volume DECREASE
• Air pressure INCREASE
• Air flows out
• Rib cage movements can contribute
• Superior bigger, air in
• Inferior smaller, air out

68
Common Methods of Reporting Gas Pressure
Table 231
69
Pressure and Volume Changes with Inhalation and
Exhalation
Figure 2315
70
1. Pulmonary Ventilation
71
Factors influencing pulmonary ventilation

• 1. Airway resistance
• Diameter of bronchi
• Obstructions
• 2. Alveolar surface tension
• Surfactant (Type II cells) reduces alveoli
  surface tension
• Allow inflation
• Respiratory distress syndrome
• Too little surfactant ? requires great force to
  open alveoli to inhale

72
Factors influencing pulmonary ventilation

• 3. Compliance
• Effort required to expand lungs and chest
• High compliance expand easily, normal
• Low compliance resist expansion
• Compliance affected by
• 1. CT structure
• 2. Alveolar Expandability
• 3. Mobility of thoracic cage

73
Factors influencing pulmonary ventilation

• 3. Compliance affected by
• 1. CT structure
• Loss of elastin/replacement by fibrous tissue
  Decrease compliance
• Emphysema
• respiratory surface replaced by scars
• Decrease elasticity Decrease compliance
• Loss of surface for gas exchange
• 2. Alveolar Expandability
• - Increase surface tension (decr.
  Surfactant)
• decrease compliance
• - Fluid (edema) decrease compliance

74
Factors influencing pulmonary ventilation

• 3. Compliance affected by
• 3. Mobility of thoracic cage
• - less mobility decrease compliance

75
Inspiration

• Inhalation involves contraction of muscles to
  increase thoracic volume
• 1. Quite breathing eupnea
• Diaphragm moves 75 of air
• External intercostals elevate ribs, 25more
• 2. Forced breathing hyperpnea
• Maximum rib elevation increases respiratory
  volume 6x
• Serratus anterior, pectoralis minor, scalenes,
  sternocleidomastoid

76
The Respiratory Muscles
Figure 2316a, b
77
Expiration

• 1. Eupnea
• Passive, muscles relax, thoracic volume decrease
• 2. Hyperpnea
• Abdominal muscles (obliques, transversus, rectus)
  contract forcing diaphragm up, thoracic volume
  further decrease

78
The Respiratory Muscles
Figure 2316c, d
79
Respiratory Volumes and Capacities
Figure 2317
80
4 Pulmonary/Respiratory Volumes

• Resting tidal volume
• The amount of air inhaled or exhaled with each
  breath under resting conditions
• Expiratory reserve volume (ERV)
• Amount of air that can be forcefully exhaled
  after a normal tidal volume exhalation
• Residual volume
• Amount of air reaming in the lungs after a forced
  exhalation
• Inspiratory reserve volume (IRV)
• Amount of air that can be forcefully inhaled
  after a normal tidal volume inhalation

81
4 Respiratory Capacities

• Inspiratory capacity (IC)
• Maximum amount of air that can be inspired after
  a normal expiration
• IC Tidal volume IRV
• Functional residual capacity (FRC)
• Volume of air remaining in the lungs after a
  normal tidal volume expiration
• FRC ERV RV

82
4 Respiratory Capacities

• Vital capacity
• Maximum amount of air that can be expired after a
  maximum inspiratory effort
• VC TV IRV ERV
• Total lung capacity
• Maximum amount of air contained in lungs after a
  maximum inspiratory effort
• TLC TV IRV ERV RV

83
Respiratory Volumes and Capacities

• A breath one respiratory cycle
• Respiratory rate breaths/min
• At rest 18-20
• Respiratory Minute Volume (RMV/MRV) respiratory
  rate X tidal volume, 6 L
• Not all air reaches alveoli, some air remains in
  conduction portions anatomic dead space
• 1ml/lb body weight
• Alveolar ventilation air reaching alveoli/min
• At rest 4.2 L
• Both tidal volume and respiratory rate are
  adjusted to meet oxygen demands of body

84
Respiratory Minute Volume

• Amount of air moved per minute
• Is calculated by
• respiratory rate ? tidal volume
• Measures pulmonary ventilation

85
Alveolar Ventilation

• Amount of air reaching alveoli each minute
• Calculated as
• tidal volume anatomic dead space ? respiratory
  rate

86
In pneumonia, fluid accumulates in the alveoli of
the lungs. How would this accumulation affect
vital capacity?

1. increase vital capacity
2. decrease vital capacity
3. increase breathing rate, with no effect on vital
   capacity
4. decrease tidal volume, with no effect on vital
   capacity

87
2. Gas Exchange
88
Composition of Air

• Nitrogen (N2) about 79
• Oxygen (O2) about 21
• Water vapor (H2O) about 0.5
• Carbon dioxide (CO2) about 0.04
• Trace inert gasses
• Partial pressure of gas concentration in air

89
2. Gas Exchange

• Depends on
• 1. Partial Pressures of the gases
• The pressure contributed by each gas in the
  atmosphere
• All partial pressures together add up to 760 mm
  Hg
• also known as Atmospheric Pressure
• Gasses follow diffusion/concentration gradients
  to diffuse into liquid
• Rate depends on partial pressure and temperature

90
Henrys Law
Figure 2318
91
2. Gas Exchange

• 1. High Altitude Sickness
• Decrease PP O2 at high altitude ? decrease
  diffusion into blood
• 2. Decompression Sickness
• PP of air gasses high underwater
• High amounts of N2 diffuses in blood
• If pressure suddenly decreases
• N2 leaves blood as gas causing bubbles ? damage
  pain
• Hyperbaric chambers are used to treat

92
Efficiency of Gas Exchange/Diffusion at the
Respiratory Membrane

• Due to
• 1. Substantial differences in partial pressure
  across the respiratory membrane
• Distances involved in gas exchange are small
• 3. O2 and CO2 are lipid soluble
• 4. Total surface area for diffusion is large
• Coordination of blood and air flow
• - Increase blood to alveoli with increase O2

93
Respiratory Processes and Partial Pressure
Figure 2319
94
2. Gas Exchange

• In Lungs
• PP O2
• High in alveoli and Low in capillary (blood)
• Diffuse into capillaries
• PP CO2
• Low in alveoli and High in capillary (blood)
• Diffuse into alveoli
• In Tissues
• Pressure and flow reversed
• O2 into tissues
• CO2 into capillary

95
3. Gas Transport
96
3. Gas Transport

• A. Transport of Oxygen
• 1.5 dissolved in plasma
• Most bound to iron ions on heme of hemoglobin in
  erythrocytes
• 4 O2/HB, 280 million Hb/RBC 1 million O2/RBC
• Hemoglobin saturation hemes bound to O2
• 97.5 at alveoli
• At high PP O2 hemoglobin binds O2
• At low PP O2 hemoglobin drops O2
• Carbon Monoxide Poisoning CO out-
• Compete O2 for binding to Hb, even at low PP CO
• Causes suffocation (no O2)

97
Oxyhemoglobin Saturation Curve
Figure 2320 (Navigator)
98
3. Gas Transport

• A. Transport of Oxygen
• Other factors that affect Hb saturation
• Bohr effect Affect of pH
• Hb releases O2 in acidic pH
• High CO2 creates carbonic acid
• Temperature
• - Hb releases O2 in high temperature
• BPG (2,3 bisphosphoglycerate)
• Produced by healthy RBC during glycolysis
• Increase BPG Increase O2 release
• Pregnancy
• - Fetal Hb increase O2 binding

99
pH, Temperature, and Hemoglobin Saturation
Figure 2321
100
The Bohr Effect

• Caused by CO2
• CO2 diffuses into RBC
• an enzyme, called carbonic anhydrase, catalyzes
  reaction with H2O
• produces carbonic acid (H2CO3)
• Carbonic acid (H2CO3)
• dissociates into hydrogen ion (H) and
  bicarbonate ion (HCO3)
• Hydrogen ions diffuse out of RBC, lowering pH

101
Fetal and Adult Hemoglobin
Figure 2322
102
Fetal and Adult Hemoglobin

• The structure of fetal hemoglobin
• differs from that of adult Hb
• At the same PO2
• fetal Hb binds more O2 than adult Hb
• which allows fetus to take O2 from maternal blood

103
KEY CONCEPT

• Hemoglobin in RBCs
• carries most blood oxygen
• releases it in response to low O2 partial
  pressure in surrounding plasma
• If PO2 increases, hemoglobin binds oxygen
• If PO2 decreases, hemoglobin releases oxygen
• At a given PO2
• hemoglobin will release additional oxygen
• if pH decreases or temperature increases

104
3. Gas Transport

• Transport of Carbon Dioxide
• 1. 70 as Carbonic acid
• - In RBCs and plasma
• Carbonic anhydrase in RBCs catalyze reaction with
  water
• CO2 H2O ?? H2CO3 ?? H HCO3-
• Reaction is reversed at lungs
• 23 as carbaminohemoglobin
• CO2 bound to amino groups of Hb
• 3. 7 dissolved in plasma as CO2

105
Carbon Dioxide Transport
Figure 2323 (Navigator)
106
KEY CONCEPT

• CO2 travels in the bloodstream primarily as
  bicarbonate ions, which form through dissociation
  of carbonic acid produced by carbonic anhydrase
  in RBCs
• Lesser amounts of CO2 are bound to Hb or
  dissolved in plasma

107
Summary Gas Transport
Figure 2324
108
As you exercise, hemoglobin releases more oxygen
to your active skeletal muscles than it does when
the muscles are at rest. Why?

1. Oxygen is released more readily at higher
   temperatures.
2. Oxygen is released more readily at higher pH.
3. Oxygen is released more readily at lower
   temperatures.
4. B and C are correct.

109
How would blockage of the trachea affect the
blood pH?

1. increase blood pH
2. decrease blood pH
3. rapid fluctuations
4. no effect

110
Regulation of Respiration
111
Respiratory Centers and Reflex Controls
Figure 2326
112
Regulation of Respiration

• Respiratory homeostasis requires that
• Diffusion rates at peripheral capillaries (O2 in,
  CO2 out) and alveoli (CO2 out, O2 in) must match
• Regulation
• Autoregulation
• Neural Regulation

113
Regulation of Respiration

• 1. Autoregulation
• Lung perfusion
• - Blood flow is lungs is redirected to alveoli
  with high partial pressure of O2
• Alveolar ventilation
• - Alveoli with high partial pressure of CO2
  receive increased air flow

114
Regulation of Respiration

• Neural Regulation
• Respiratory Rhythmicity Centers
• Located in the medulla oblongata
• Control the basic pace and depth of respiration
• DRG (Dorsal Respiratory Group)
• Controls diaphragm and external intercostal
  muscles on the every breath
• Serves as the pacesetting respiratory center
• Active for 2 sec, inactive for 3 sec
• VRG (Ventral Respiratory Group)
• - Controls accessory muscles during forced
  breathing

115
Quiet Breathing
Figure 2325a
116
Regulation of Respiration

• 2. Neural Regulation
• B. Respiratory Centers
• Located in the pons
• Influence and modify activity of the DRG and VRG
• to fine tune breathing rhythm
• prevent lung over-inflation
• Monitor input from sensory receptors to trigger
• appropriate reflex ? alter respiratory rate and
  depth of respiration to satisfy gas exchange
  needs
• Apneustic Center
• Stimulates the DRG for inhalation
• Helps increase intensity of inhalation
• Responds to lung inflation signals from sensory
  receptors

117
Regulation of Respiration

• 2. Neural Regulation
• Respiratory Centers
• 2. Pneumotaxic Center
• Inhibits the apneustic center to allow exhalation
• Modifies the pace set by DRG and VRG
• Increased signaling
• increase respiratory rate by decreasing duration
  of inhalation
• Decreased signaling
• decrease respiratory rate but increase depth by
  allowing apneustic center to signal DRG for
  greater inhalation

118
Regulation of Respiration

• 2. Neural Regulation
• Respiratory Reflexes
• Respiratory centers modify activity based on
  input from receptors
• Chemoreceptors
• - monitor CO2, O2, and pH in blood and CSF
• Baroreceptors
• - monitor blood pressure in aorta and carotid
  artery
• Stretch receptors
• - monitor inflation of the lungs (Hering-Breuer
  Reflex)

119
Regulation of Respiration

• 2. Neural Regulation
• Respiratory Reflexes
• Pulmonary irritant receptors
• - monitor particle sin respiratory tracts and
  trigger cough or sneeze
• Other
• - pain, temperature, and visceral sensations can
  trigger respiratory reflexes

120
The HeringBreuer Reflexes

• 2 baroreceptor reflexes involved in forced
  breathing
• inflation reflex
• prevents overexpansion of lungs
• deflation reflex
• inhibits expiratory centers
• stimulates inspiratory centers during lung
  deflation

121
KEY CONCEPT

• A basic pace of respiration is established
  between respiratory centers in the pons and
  medulla oblongata, and modified in response to
  input from
• chemoreceptors
• baroreceptors
• stretch receptors
• In general, CO2 levels, rather than O2 levels,
  are primary drivers of respiratory activity

122
3 Effects of Aging on the Respiratory System

• Elastic tissues deteriorate
• reducing lung compliance
• lowering vital capacity
• Arthritic changes in rib cage
• Decrease mobility of chest movements
• decrease respiratory minute volume
• Emphysema
• Decrease gas exchange
• Higher risk if exposed to respiratory irritants
  (e.g., cigarette smoke, dusty jobs)

123
Respiratory Performance and Age
Figure 2328
124
What effect would exciting the pneumotaxic
centers have on respiration?

1. shorter breaths
2. rapid breathing rate
3. no effect
4. A and B

125
Are peripheral chemoreceptors as sensitive to
levels of carbon dioxide as they are to levels of
oxygen?

1. Yes.
2. No, they are more sensitive to oxygen levels.
3. No, they are more sensitive to carbon dioxide
   levels.
4. The sensitivities can not be compared.

126
Johnny is angry with his mother, so he tells her
that he will hold his breath until he turns blue
and dies. Should Johnnys mother worry?

1. Yes
2. No

127
SUMMARY

• 5 functions of the respiratory system
• gas exchange between air and circulating blood
• moving air to and from exchange surfaces
• protection of respiratory surfaces
• sound production
• facilitating olfaction
• Structures and functions of the respiratory
  tract
• alveoli
• respiratory mucosa
• lamina propria
• respiratory defense system
• Structures and functions of the upper respiratory
  system
• the nose and nasal cavity
• the pharynx
• Structures and functions of the larynx
• cartilages and ligaments
• sound production
• the laryngeal musculature

128
SUMMARY

• Structures and functions of the trachea and
  primary bronchi
• Structures and functions of the lungs
• lobes and surfaces
• the bronchi
• the bronchioles
• alveoli and alveolar ducts
• blood supply to the lungs
• pleural cavities and membranes
• Respiratory physiology
• external respiration
• internal respiration
• Pulmonary ventilation
• air movement
• pressure changes
• the mechanics of breathing
• respiratory rates and volumes
• Gas exchange
• the gas laws
• diffusion and respiration

129
SUMMARY

• Gas pickup and delivery
• partial pressure
• oxygen transport (RBCs and hemoglobin)
• carbon dioxide transport
• Control of respiration
• local regulation (lung perfusion, alveolar
  ventilation)
• respiratory centers of the brain
• respiratory reflexes
• voluntary control of respiration
• Aging and the respiratory system